Hip dysplasia may not be obvious in newborns, but the disorder may already be affecting babies' development. And the sooner parents and caregivers get an evaluation and treatment, the easier the fix, according to Dr. Andrew Abramowitz, a board-certified orthopedic surgeon at MedStar Franklin Square Medical Center who trained in pediatric orthopedics.

What is pediatric hip dysplasia and how common is it?

Hip dysplasia (developmental dysplasia of the hip or DDH) is a spectrum of abnormalities of the ball and socket joint of the hip. It occurs in one in every 1,000 live births. Although it is often present at birth, it may develop during the first year of life. Babies whose legs are swaddled with the hips and knees straight are at higher risk for developing hip dysplasia after birth.

In all cases of hip dysplasia, the socket is shallow, meaning the ball of the thigh bone (femur) cannot firmly fit into the socket. The degree of dysplasia varies based on the looseness between the ball and the socket. In the most severe cases, the ball is dislocated from the socket. In moderate cases, the ball is dislocatable, meaning it lies within the socket but can be easily pushed out of the socket on a physical examination. In the mildest cases, the ball is subluxatable, meaning that it is simply loose in the socket but it will not dislocate.

If the ball does not stay securely within the confines of the socket, the hip joint cannot develop normally. If the ball is out of the socket for any length of time, the femoral head can become deformed and the socket remains shallow. Ultimately, the deformed hip joint can lead to the development of arthritis in early adolescence or adulthood.

What causes it or increases a child's chances of having it?

DDH has no one specific cause. It is more common in girls, first-born children (the uterus is small with limited room for the baby to move), babies born in the breech position (feet up by the shoulders), oligohydramnios (low amniotic fluid level) and those with a family history of DDH (parents or siblings). The left hip tends to be more frequently involved than the right.

What are the symptoms, and does the condition hurt?

There are often no specific symptoms that the baby will exhibit or that the family will elicit. However, if your baby has unequal leg lengths, uneven skin folds on the thigh or less mobility of one or both hips, you should contact your physician. In children of walking age, you may see a limp, unilateral toe walking or a waddling-type gait. DDH does not cause the child pain.

How is it diagnosed and treated?

DDH is diagnosed by a doctor's clinical exam where they will perform specific maneuvers to see if the hip dislocates or not. Often, in children less than 6 months of age, an ultrasound will be done to confirm the physician's exam. Certain newborns who are at high risk for DDH (first-born, female, breech babies) yet have a normal clinical exam, are also screened by ultrasound.

DDH treatment depends on the child's age. Most children between birth and 6 months of age can be treated with a Pavlik harness. This soft positioning device helps guide the hip and hold it in the optimum position while allowing easy diaper care and free movement of the legs. It helps tighten the ligaments around the hip and aids in normal hip socket development. The harness is worn anywhere from one to three months, depending on the type of dysplasia. In dislocated hips, it is normally worn full time for four to six weeks until the hip is located and stable and then part time for another four to six weeks. There will be frequent visits to monitor the fit of the harness as well as ultrasounds to document the hip's position. Once the harness is removed the child is followed until the hip is normal both clinically and by X-ray. Further bracing, and sometimes surgery, is necessary to help stimulate and/or correct socket development.

If the hip will not stay in position using the harness, your doctor may try a fixed abduction brace that will keep the baby's legs in a better position. About 80-90 percent of hips treated with the harness locate and stabilize. For those hips that do not (as well as those children initially seen between 6 and 18 months), a closed reduction may be necessary. This is where the child is taken to the operating room and the hip is located while the child is under anesthesia. Once asleep, dye is put into the hip joint and the femoral head is guided into the socket manually. Once in proper position, a spica (body) cast is applied to hold the hip in position. The cast is usually worn for 3 months with a cast change under anesthesia at six weeks. After the cast is removed, the child is followed until the hip is normal clinically and by X-ray. Sometimes further bracing and/or surgery is necessary to stimulate socket development.

If closed reduction fails in children between 6 and 18 months (and in children older than 18 months upon presentation), we proceed to an open reduction of the hip. In this procedure, an incision is made to open the baby's hip joint and remove the obstacles to reduction. In addition, the capsule is tightened. In some cases, the baby's thigh bone will need to be shortened in order to get the hip to be located into the socket without undue tension. After the surgery, the baby wears a spica cast for approximately six weeks. In children older than age 2, oftentimes surgery is necessary to improve socket development as well, which is done at the time of open reduction.

Are there any lasting effects?

Children treated with casting may have some delays in walking, but once the cast is removed, walking development proceeds normally. If diagnosed early and treated successfully, most children have no residual issues from their DDH and they develop a normal hip joint and can function without limitations. However, left untreated, DDH usually leads to painful arthritis by early adulthood requiring hip replacement surgery. If DDH is unilateral and untreated, it may produce a leg length difference as well.